GREGORi': FISH SKULLS 



341 



islands of the tropical Pacific, is said by Jordan and Evermann (Hawaiian Fishes, 1905, p. 

 453) to be closely related to the Scorpsenidae but differs in the compressed, deep body and 

 vestigial pelvic fins. Several bones of the head are strongly armed, the preopercular and 

 inttropercular bear strong spines directed downward. 



Triglids. — In the gurnards (Triglidae) and their allies the surface bones of the cheek 

 (Figs. 218-221), especially the suborbitals, have become enlarged into two great flat armor 

 plates, one on each side; these together with the heavily armored skull-roof form a strong 

 shield for the whole head. Although the orbits are widely open in the dried skull, the eyes 

 are perhaps protected by a tough sclerotic coat, cornea and surrounding skin; but, as 

 remarked above, the eyes seem to have a dominant role in the scorpaenoid group and 

 apparently the fish must depend upon its visual alertness to avoid injury to its eyes. 



The outer surface of all the bones of the cheek-plate is covered with sharply raised 

 ridges that radiate from the ossific centers. In Prionoius and other genera the edge of 



Dactylopterus volitans 



Fig. 222. Dactylopterus (Cephatacantkus). 



each ridge bears a single row of more or less sharp, thorn-like projections, which are so small 

 as to be seen as individuals only with a pocket-lens. As their tips are all in nearly continuous 

 planes these denticles impart a smooth, velvet-like appearance and sandpaper-like feel to 

 the surface. They are enlarged in some places, notably at the front edge of the lacrymal, 

 into a short-toothed, comb-like edge. Besides the minute denticles there is a fairly large 

 spike on the posterior border of the preopercular, two smaller ones on the opercular and one 

 above the orbit, others on the skull-top behind the orbit. By comparison with other scor- 

 psenoids it seems evident that the raised radiating ridges of the cheek-plates represent an 

 extreme emphasis of the radiating trabeculse of less specialized forms and that the minute 

 denticles on the surface are comparable with the villous outgrowths on the surface of the 

 trabecular ridges in the peculiar cottoid Enophrys {Aspicottus) (see p. 339). Detailed 

 and repeated comparisons of the surface ridges and denticles of the triglids with those of 



